Method of and apparatus for precooling concrete mix ingredients



Aug. 2, 1966 E. J. GOLDFARB METHOD OF AND APPARATUS FOR PRE-COOLING CONCRETE MIX INGREDIENTS Filed Feb. 5, 1965 INVENTOR. [few/A Jozaama United States Patent Office 3,263,436 Patented August 2, 1966 3,263,436 METHOD OF AND APPARATUS FOR PRE- QOOLING CONCRETE MIX INGREDIENTS Erwin J. Goldl'arb, Champaign, Ill., assignor to Koehring Company, Milwaukee, Wis, a corporation of Wisconsin Filed Feb. 5, 1965, Ser. No. 430,640 11 Claims. (Cl. 62-100) The invention relates to the cooling and drying of granule material, and it is concerned more particularly with the preparation of cooled granular ingredients for a concrete mix.

Various methods and types of apparatus have heretofore been suggested for cooling ingredients of a concrete mix, particularly aggregate and sand, before they are mixed with the proper quantities of cement and water. The practice of pro-cooling the ingredients of a concrete mix :is commonly employed for large construction project-s such as the building of water dams where large quantities of concrete mix are poured at a time. By pre-cooling the ingredients the temperature of the batch can be kept sulficiently low so that the heat which is generated by the curing of the cement will not raise the temperature of the poured mass beyond permissible limits.

In certain types of apparatus which have heretofore been suggested for the pre-cooling of concrete mix ingredients, a relatively large quantity of the ingredients is accumulated in a tank or silo, and cooling is effected by vacuum evaporation of moisture from the ingredients within the tank. However, these apparatus of the prior art have several shortcomings. For instance, in order to cool sand it has heretofore been diflicult to lower the temperature of the entire body of sand uniformly, that is, to avoid the formation of cold spots where the sand may freeze and become lumpy, and the formation of warm spots where the temperature remains relatively high due to lack of sufiicient vacuum. Also, if the apparatus has an evacuated cooling chamber into which the sand is passed through a restricted opening from a storage chamber, some sand is carried out with the vapor causing rapid wear to the ducts due to its abrasive effect at high velocity.

A further and most serious disadvantage of the mentioned prior art apparatus is the difliculty of controlling its output so that a desired quantity of pre-cooled ingredients for one or several batches will be available if and when it is needed during the progress of the construction project. Operation of the cooling apparatus must be carefully timed with reference to other phases of the construction work, so that upon completion of the cooling operation all of the cooled material can be immediately discharged from the tank or silo, worked into a pourable batch or batches, hauled to the pouring site and poured. Should the discharge of the cooled ingredients from the tank or silo be delayed due to some unforeseen irregularity in the work schedule of the project, the cooled ingredients will have to be left in the tank or silo but will not stay cool very long. On a warm summer day only a few hours may suffice to bring the ingredients in the tank or silo back to a temperature which is no longer low enough to obtain the desired low temperature of the batch. If a cooled quantity of sand has been permitted to remain within the tank long enough to cause an objectionable temperature rise beyond a permissible level, it becomes necessary to re-cool the sand before it can be used. This has heretofore entailed some dilficulty because it has been necessary, at least in some vacuum type cooling apparatus of the prior art, to withdraw the entire quantity of accumulated sand from the bottom of the tank and to then reload it into the tank at the top.

Generally, it is an object of the present invention to provide an improved method of cooling moist granular material by vacuum evaporation of moistre therefrom, the improved method being such as to avoid the hereinbefore outlined shortcomings :of the prior art, particu larly in the matter of timing the cooling of sand in relation to other phases of a construction project.

Another object of the invention is to provide an improved apparatus for pre-cooling a relatively large quantity of sand for a concrete mix, and particularly to cool the sand gradually and uniformly throughout its entire mass.

A further object of this invention is to provide an improved cooling apparatus of the aforementioned character wherein a predetermined quantity of sand may be cooled to a desired temperature and then re-cooled, after a warm-up, without first unloading the sand from, and then reloading it into the apparatus.

A further object of the invention is to provide an improved cooling apparatus of the aforementioned character which may be operated intermittently to complete an operating cycle, that is, whose operating cycle may be interrupted at any time before the sand has been cooled to a desired final temperature, and whose operation may be resumed at any time to complete the operating cycle without first unloading the sand from and then reloading it into the apparatus.

A still further object of the invention is to provide an improved cooling apparatus of the above mentioned character which has a single tank of minimum size for storing and cooling a maximum quantity of granular ingredients for a concrete mix.

These and other objects and advantages are attained by the present invention, various novel features of which will become apparent from the description herein and the accompanying drawings showing a preferred embodiment of the invention.

Referring to the drawings:

FIG. 1 is a sectional schematic side view of a sand cooling apparatus embodying the invention;

FIG. 2 is a sectional view on line IIII of FIG. 1; and

FIG. 3 is an elevational view of the lower end of the apparatus shown in FIG. 1, the view of FIG. 3 being taken partly in section on line IIIIII of FIG. 1.

The principal components of the apparatus shown in FIG. 1 are an upright, silo type tank 1, a bucket elevator 2 within the tank, and evacuating pump means for the tank comprising a primer vacuum pump 3 and a steam jet vacuum booster pump 4.

Suitably mounted within the tank 1 are two relatively opposed longitudinal partitioning walls 6 and '7 (FIG. 1), and a pair of relatively opposed longitudinal partitioning walls 8 and 9 (FIG. 2) in right angle relation to the partitioning walls 6 and 7. These partitioning walls are connected with each other along their adjacent edges, as by welding, and they divide the interior of the tank 1 into a sand storage space 10 which extends substantially the full length of the tank except for some head rooms at the top and bottom, and into a conveyor casing 11 which encloses the bucket elevator 2. As shown in FIG. 1, the partitioning Wall 6 is solid throughout its length and terminates at its lower end at a distance above an arcuately curved bottom wall portion 12 of the tank. The spacing between the lower end of the partitioning wall 6 and the adjacent upper edge of the bottom wall portion 12 of the tank affords a lower passage 13 which connects the sand storage space 10 at its lower end in sand transmitting relation with the lower end of the conveyor casing 11.

At its upper end the partitioning wall 6 terminates at a vertical spacing below an overlying top wall portion 14 of the tank 1, thereby providing an upper passage 16 through which sand may be returned from the conveyor casing 11 to the sand storage space 10. An inlet neck 17 at the upper end of the tank 1 is normally closed in conventional manner by a removable cover 18, and an outlet neck 19 at the lower end of the tank is normally closed by removable closure means of conventional construction, such as a pair of power actuated gate plates 21 and 22 (FIG. 3).

Flow of sand from the storage space into the conveyor casing 11 through the lower passage 13 is controlled by a clam shell gate 23 of conventional construction, a pair of pneumatic actuating cylinders 24 and 26 being connected with the gate 23 as indicated in FIG. 3.

The bucket elevator 2 comprises an endless chain or belt type conveying element 27 which is trained over upper and lower sprocket wheels or rollers 28 and 29. The conveying element 27 carries a series of buckets 31 which are mounted on the conveying element in conventional manner at proper spacings from each other. A suitable power transmitting mechanism, not shown, is connected with one of the sprocket wheels or rollers 28, 29 and operable to drive the conveying element in the direction of the arrows indicated in FIG. 1.

Duct means are connected interiorly of the tank 1 in vacuum communicating relation with the conveyor casing 11 and with the sand storage space 10, such duct means comprise an annular main duct 32 which extends peripherally of the tank at a relatively short distance above the lower end of the latter, and a series of channel iron rings 33 which extend peripherally of the tank at vertical spacings from each other above and below the main duct 32.

Referring to FIGS. 1 and 3, the main duct 32 is formed by an annular sheet metal structure of generally channel shaped cross section, ring shaped upper and lower flanges 34, 36 being welded along their outer peripheral edges to the inner surface of the tank wall, and the inner peripheral edges of the flanges 34, 36 being connected by a generally vertical, somewhat bowed web member 37. The conveyor casing 11 is positioned off-center within the tank 1 as shown in FIG. 2, and the flange rings 34 and 36 bridge the space between the vertical wall of the tank 1 and the confronting vertical wall 7 of the elevator casing to which they are connected air tight, as by welding. The vertical web portion 37 of the main duct 32 merges with the side walls 8 and 9 of the conveyor casing 11 and is connected air tight thereto, as by welding. Apertures 38 and 39 in the vertical casing wall 7 between the flange rings 34 and 36 connect the main duct 32 in vacuum communicating relation with the interior of the conveyor casing 11.

Each of the channel iron rings 33 comprises a hori- Zontal annular web portion and depending radially inner and outer vertical flanges. The webs of the channel irons 33 like the flanges 34, 36 of the main duct 32 bridge the space between the vertical wall of the tank 1 and the confronting vertical wall 7 of the conveyor casing 11 to which they are connected air tight, as by welding, immediately below the depending radially inner flange of each channel iron ring 33 an aperture 41 is formed in the vertical wall 7 of the conveyor casing 11. The apertures 41 connect the interior of the conveyor casing 11 in vacuum communicating relation with the annual space between the web and flanges of each channel ring 33, and these annular spaces in turn are exposed in vacuum communicating relation to the sand storage space 10 of the tank 1.

Exhaust pump means comprising the primer vacuum pump 3 and the steam jet vacuum booster pump 4 are connected with the main duct 32 for evacuating the conveyor casing through the apertures 38, 39 of the casing wall 7, and for evacuating the sand storage space 10 through the channel irons 33 and apertures 41 of the casing wall 7. The primer vacuum pump 3 and steam jet vacuum booster pump 4 are of conventional construction and their connections with the tank 1 are controlled by a priming valve 42 and by a main valve 43, respectively. The priming valve 42 has a double acting air ram 44 by means of which it can be closed and opened, and the main valve 43 is similarly equipped with a double acting air ram 46.

An operating cycle of the apparatus shown in the drawings may be performed as follows. First, clamshell gate 23 and bottom gate plates 21, 22 are closed, and top cover 18 of the inlet neck 17 is removed. The tank is then filled through the neck 17 with sand to be cooled, the sand being taken from a stock pile and containing a normal amount of water. Ordinarily, the tank 1 will be filled to capacity, that is, until the height of the accumulated sand mass 47 approaches the upper end of the wall 6 of the conveyor casing. However, if a quantity of sand less than the full tank capacity is to be cooled, the loading of the tank may be stopped at any desired moment. Next, the top cover 18 is secured in place thereby sealing the tank vacuum tight. Priming valve 42 is then opened and sufiicient air is removed from the tank to reduce the absolute pressure in the tank down to the vapor pressure of the moisture in the sand.

When the tank pressure has been lowered to the vapor pressure of the moisture in the sand the priming valve 42 is closed and main vacuum valve 43 is opened, allowing removal of vapor. The bucket elevator 2 is then started, and the clamshell gate 23 is opened to load the elevator.

Each of the buckets 31 withdraws a relatively small quantity of sand from the lower end of the storage space 10 as the buckets pass around the lower sprocket wheel or roller 29. The withdrawn small quantities of sand are moved upward through the elevator casing and as the buckets pass around the upper sprocket wheel or roller 28 their contents are returned into the storage space 10 through the upper passage 16. In this manner portions of the accumulated sand mass 47 are successively withdrawn from one end of the elongated body of sand in the storage space 10 and the withdrawn portions are returned to the other end of said body through the conveyor casing, that is, through a passage separate from the elongated body of sand in the storage space 10. While gravitational downward motion is thus imparted to the sand in the storage space 10, the vertical position of the accumulated body of sand in the storage space remains substantially unchanged.

The moisture evaporating vacuum is communicated to the sand in the storage space 10 through the channel iron rings 33, an annular void being formed at the under side of each channel ring as the sand moves downwardly past the rings and assumes its natural angle of repose below them.

Circulation of the sand within the tank by operation of the bucket elevator while a moisture evaporating vacuum is maintained in the elevator casing and under the channel iron rings 33, is continued for a sufficient length of time to vacuum cool the entire quantity of accumulated sand within the tank to a desired temperature. Thereafter, the main vacuum valve 43 is closed and any desired quantity of cooled sand may be unloaded from the tank at the outlet neck 19. If less than the entire mass of cooled sand is to be discharged, closing of the clam shell gate 23 prior to closing of the gate plates 21, 22 will facilitate closing of the latter.

If the cooled sand is permitted to remain in the tank after the vacuum has been removed, it will gradually warm up again, the rate of its temperature rise depending on the ambient temperature. If the unloading of the tank is delayed, as for instance when a cooling cycle has been completed near the end of a working day and the sand must remain in the tank overnight, recooling of the sand which has been accumulated in the tank becomes necessary. Such recooling can be accomplished with the herein disclosed apparatu by starting the bucket elevator and placing the vacuum pumps in operation. In other words, recoolingof a quantity of sand which is stored in the tank can be accomplished without first withdrawing the entire contents of the tank from the bottom and reloading them into the tank at the top as has been necessary with some types of cooling apparatus of the prior art.

Also, if it should be desired to interrupt the cooling cycle for a certain length of time in order to coordinate the sand cooling with other phases of a construction project, this can readily be accomplished with the herein disclosed apparatus, as will be apparent from the foregoing explanations.

It should be understood that it is not intended to limit the invention to the herein disclosed form of apparatus and details of construction and operation, but that the invention includes such other forms and details as are embraced by the scope of the appended claims.

It is claimed and desire-d to be secured by Letters Patent:

1. A method of cooling moist granular material by vacuum evaporation of moisture therefrom comprising, continuously circulating a quantity of said material in an endless path within a tank and simultaneously maintaining a moisture evaporating vacuum therein.

2. A method of cooling moist granular material by vacuum evaporation of moisture therefrom comprising, accumulating an elongated body of said material within a tank, successively withdrawing portions of said body from one end thereof, returning said withdrawing portions to the other end of said body through a passage separate from said body, and maintaining a moisture evaporating vacuum within said passage while said portions of said material are returned therethrough from aid one end of said body to the other.

3. A method of cooling moist granular material by vacuum evaporation of moisture therefrom, said method comprising accumulating an elongated vertical body of said material within a tank, successively withdrawing portions of said material from the lower end and returning them to the upper end of said body through a passage within said tank separate from said body, and maintaining a moisture evaporating vacuum within said passage while said with-drawn portions of said material are returned therethrough from said lower to said upper end of said body.

4. A method of cooling moist granular material by vacuum evaporation of moisture therefrom, comprising accumulating an elongated vertical body of said material within a tank; imparting gravitational downward motion to said material by successively withdrawing portions of said body from its lower end and by returning said portions to the upper end of said body through a passage separate from said body; and maintaining a moisture evaporating vacuum in said passage while said portions are returned therethrough from said lower to said upper end of said body.

5. A method of cooling moist granular material by vacuum evaporation of moisture therefrom, comprising accumulating an elongated vertical body of said material within a tank, imparting gravitational downward motion to said accumulated material without substantially changing the vertical position of said body by successively withdrawing portions of said body from its lower end and by returning said withdrawn portions to the upper end of said body; and maintaining a moisture evaporating vacuum on said body and on said withdrawn portions thereof while the latter are returned from said lower to said upper end of said body.

6. A method of preparing cooled sand for a concrete mix; comprising accumulating a guantity of sand in an elongated vertical storage space presented by a tank interiorly partitioned into said storage space and into a passage extending from one end of said storage space to the other, imparting gravitational downward motion to the sand in said storage space by successively withdrawing portions thereof from said lower end and returning them to the upper end of said storage space through said passage; maintaining a moisture evaporating vacuum in said storage space and passage and simultaneously maintaining said downward motion of said sand in said storage space for a suiiicient length of time to vacuum cool the entire quantity of accumulated sand within said tank to a desired temperature; and discharging desired quantities of sand from said storage space after it has been cooled to said desired temperature.

7. A method of preparing cooled sand for a concrete mix as set forth in claim 6 and wherein said vacuum is maintained in said storage space by exhausting the latter at a point above the accumulated sand therein and at vertically spaced points below the top of said accumulated sand.

3. Apparatus for pre-cooling sand for a concrete mix comprising, a tank; partitioning means within said tank dividing the interior of the latter into an elongated storage space and into a conveyor casing extending along said storage space and communicating therewith at its opposite ends; movable conveying means within said casing operable to successively withdraw portions of sand accumulated within said storage space from one end of the latter and to return said portions to said storage space at its other end; exhaust duct means connected interiorly of said tank in vacuum communicating relation with said conveyor casing, exhaust pump means operatively connected with said duct means for evacuating said conveyor casing sufficiently to effect moisture evaporation from and cooling of sand moved through said conveyor casing by said conveying means, and removable closure means operatively connected with inlet and outlet apertures of said tank for the admission and emission of sand to and from said tank.

9. Apparatus as set forth in claim 8 and further comprising a plurality of circumferential exhaust channels for said storage space secured within said tank in vertically spaced relation to each other and connected in vacuum communicating relation with said conveyor casing.

10. Apparatus for pre-cooling sand for a concrete mix comprising, an upright tank, partitioning means within said tank dividing the interior of the latter into an upright storage space, an upright conveyor casing extending along said storage space, a lower passage connecting said storage space at its lower end in sand transmitting relation with the lower end of said conveyor casing, and an upper passage connecting said conveyor casing at its upper end with the upper end of said storage space; an endless bucket carrying conveying element operatively mounted within said conveyor casing in sand receiving relation to said lower passage and in sand delivering relation to said upper passage; duct means connected interiorly of said tank in vacuum communicating relation with said conveyor casing and storage space; exhaust pump means operatively connected with said duct means for evacuating said conveyor casing and storage space sufiiciently to effect moisture evaporation from and cooling of sand circulated through said conveyor casing and storage space by operation of said conveying element; and removable closure means operatively connected with inlet and outlet apertures of said tank for the admission and emission of sand to and from said tank.

11. Apparatus as set forth in claim 10 and further comprising movable gate means mounted within said tank at the lower end of said storage space and operable to open and close said lower passage; said outlet opening of said tank communicating with said lower passage in underlying relation with said gate means.

References Cited by the Examiner UNITED STATES PATENTS 2,525,581 10/1950 Bierman 62268 3,099,138 7/1963 Hightower 62-100 3,108,448 10/1963 Hightower 62100 3,150,496 9/1964 Hightower 34-15 WILLIAM J. WYE, Primary Examiner. 

1. A METHOD OF COOLING MOIST GRANULAR MATERIAL BY VACUUM EVAPORATION OF MOISTURE THEREFROM COMPRISING, CONTINUOUSLY CIRCULATING A QUANTITY OF SAID MATERIAL IN AN ENDLESS PATH WITHIN A TANK AND SIMULTANEOUSLY MAINTAINING A MOISTURE EVAPORATING VACUUM THEREIN. 